It is highly desirable to detect malignancies in human tissue at the earliest possible date. Certain types of tissue when changing from normal to malignant, pass through an intermediate stage in which the tissue cells are not actually malignant but have a strong potential to become malignant. Such pre-malignant states are well known to exist in the gastrointestinal tract (i.e., esophagus, stomach and colon). Surveillance examinations are now more or less routinely performed to detect both pre-malignant and early malignant conditions.
Currently, the preferred diagnostic method for examining the gastrointestinal tract involves the use of an endoscope to detect polyps or malignant lesions at an early stage. In the colon for instance, it is now known that most if not all malignancies arise in pre-existent polyps. Polyps may be hyperplastic, adenomatous or malignant. Hyperplastic polyps consist of normal tissue and are therefore benign. Adenomatous polyps consist of abnormal tissue but are believed to be precursors of malignant tumors. With currently available techniques, it is often necessary to remove the polyp by biopsy or, if necessary, surgery.
Thus, there is a need for a reliable diagnostic procedure that would enable medical personnel to determine instantaneously the nature of such polyps and other pre-malignant lesions of the gastrointestinal tract and other parts of the body.
It is well-known that laser induced fluorescence can be used to distinguish normal from abnormal tissue. Fluorescence spectroscopy has been used in the gastrointestinal tract to detect cancerous conditions but, in the past, this has involved pre-treatment with a fluorescent agent (i.e., hematoporphyrin derivative) which causes tissue to fluoresce. However, hematoporphyrin derivative causes side effects which greatly reduce its utility for clinical purposes. The present invention provides a laser induced fluorescence spectroscopic system which does not require the administration of any exogenous agent to induce fluorescence and which can be used with an optical fiber inserted through a conventional endoscope to examine the surface of the colon or other gastrointestinal viscus and reliably distinguish adenomatous from normal tissue.